This invention relates to a crimp terminal and a wire fixing structure in a crimp terminal.
Usually, a wire used in a wire harness for installation on a vehicle has a crimp terminal connected to its distal end so that the wire can be easily electrically connected to an equipment or other wiring.
FIG. 5 shows a related crimp terminal for connection to a connector.
This crimp terminal 1 is formed by pressing a metal sheet into a predetermined shape, and includes a fitting connection portion 2 adapted to be fittingly supported in a terminal insertion hole in a connector housing so as to be fittingly connected to a terminal of a mating connector, and a wire crimping portion 4 for being connected to a distal end portion of the wire 3.
Generally, the wire crimping portion 4 includes a sheath fixing portion 5 having a pair of sheath press-fastening piece portions 5b and 5c which extend respectively from opposite side edges of a sheath mounting portion (a bottom plate portion) 5a extending from the fitting connection portion 2 so as to be press-fastened onto a sheath portion 3a of the wire 3 placed on the sheath mounting portion 5a to thereby fix the sheath portion 3a, and a crimping connection portion 7 for being electrically connected to that portion (end portion) of a conductor portion 3b of the wire 3 exposed at a distal end of the sheath portion 3a (see, for example, JP-A-2000-251961).
In the illustrated sheath fixing portion 5, the pair of sheath press-fastening piece portions 5b and 5c are tapering at their opposed side edges as at 6, that is, are decreasing in width gradually toward their distal ends, so that their distal end portions are not superposed together.
In the crimping connection portion 7, a pair of conductor press-fastening piece portions 7b and 7c extending respectively from opposite side edges of a conductor support portion 7a integral with the sheath mounting portion 5a are press-fastened onto the conductor portion 3b placed on the conductor support portion 7a, thereby crimpingly connecting the crimping connection portion 7 to the conductor portion 3b. 
In the sheath fixing portion 5 of the related crimp terminal 1 shown in FIG. 5, the pair of sheath press-fastening piece portions 5b and 5c are offset from each other so that their distal end portions will not be superposed together. Therefore, when the pair of sheath press-fastening piece portions 5b and 5c are press-fastened onto the sheath portion 3a of the wire 3, pressing loads (shearing loads) f1 and f2 applied respectively from these portions 5b and 5c to the wire 3 act respectively in opposite directions, and have their respective effective load centers offset a distance L (equal to the pitch of the press-fastening piece portions 5b and 5c) from each other in the direction of the length of the wire 3.
However, in recent years, to meet requirements for lightweight and small-size (compact) designs of on-vehicle parts and others, wires for forming a wire harness have increasingly been formed into lightweight and smaller-diameter designs, so that the rigidity of such wires has become lower than before. Therefore, when the oppositely-directed pressing loads f1 and f2 acted on the wire with their effective load centers offset from each other as described above, there is a fear that the wire 3 might be bent and deformed between the effective load centers of these loads, thus causing defective press-fastening.
On the other hand, when the fastening force applied from the sheath press-fastening piece portions 5b and 5c is reduced so as to prevent the bending deformation of the wire 3, there is encountered a problem that the wire could not be firmly fixed because of insufficient fastening.
Furthermore, in recent years, the crimp terminal 1 also has been formed, using a metal sheet having a smaller thickness for the purpose of achieving a light weight design of the crimp terminal, and therefore the strength of the sheath press-fastening piece portions 5b and 5c of the sheath fixing portion 5 has been slightly lowered.
Therefore, in the structure of the related sheath fixing portion 5 (in which the pair of sheath press-fastening piece portions 5b and 5c are press-fastened on the sheath portion 3a in non-overlapping relation), when the wire 3 is deflected by an external force in a direction (direction T1 in FIG. 5) to unwind the sheath press-fastening piece portion 5c (disposed farther from the distal end of the wire 3 than the sheath press-fastening piece portion 5b), there is a fear that the sheath press-fastening piece portion 5c might be deformed by this external force (applied thereto through the wire 3) in a direction to loosen the winding of the sheath press-fastening piece portion 5c, so that its fixing force applied to the sheath portion 3a might be lowered.